/Engine/Source/Runtime/Landscape/Public/LandscapeEditorServices.h
Implements pure virtual function. Insertion logic is left to the user through modal drag + drop dialog.
virtual int32 GetOrCreateEditLayer ( [FName](API\Runtime\Core\UObject\FName) InEditLayerName, [ALandscape](API\Runtime\Landscape\ALandscape) * InTargetLandscape )